1. Field of the Invention
This invention relates generally to apparatus for recording and/or reproducing digital data. More particularly, the present invention relates to a rotary head type digital audio tape recorder (R-DAT) when used for recording data from a computer or the like.
2. Description of the Prior Art
In order to protect computer generated data written on a hard disc or the like, the data are sometimes transferred to a so-called data streamer (or data recorder) and are thereby recorded (or backed up) on other recording media once per day.
In most cases, a conventional data streamer is what might be called an analog audio tape recorder. Such an analog audio tape recorder, however, consumes a great quantity of the recording medium (ie. tape). Also, such a conventional data streamer has a low data rate upon recording so that it takes a lot of time for transferring and recording the data. Further, it is not easy for the analog audio tape recorder to find out the starting point of the desired recorded data.
When data from, for example, the computer is recorded on a conventional audio tape recorder, an arbitrary file mark signal is supplied thereto from the computer. Upon reproduction, the location number of the file mark for the computer designated address is searched for. Since the conventional analog audio tape recorder is so arranged as to search for the location number of the file mark by counting the reproduced signal of the file mark in the normal reproduction operation, it takes a long time to search for the desired file mark. Thus, it is difficult to search for the location number of the file mark.
A DAT (digital audio tape recorder) has been developed, as described in "ES Review", pp. 11 to 14, published on December, 1985 by Sony Corporation, Shibaura Plant: ISSN 0389-7737. Since this DAT is designed so as to record and/or reproduce a digital signal that is a digitized audio signal, it is very suitable for recording the aforesaid data.
However, generally the width of the DAT recording head is larger than the track pitch such that a portion of the preceding track is erased by the current track and data is recorded in a partially superimposed track without providing a guard band between two adjacent tracks. This will cause a problem, for example, when a portion of recorded data is reproduced, edited and recorded again. The reproducing and editing operations can be easily effected, however, it is difficult to again record the edited data.
Specifically, when data is recorded in partially superimposed tracks as set forth above, if the edited data is re-recorded, the next track in which data has been previously recorded is erased since the head width of the recording head is larger than the track width. Consequently, data to be reserved is destroyed.
To cope with the above problem, the assignee of the present invention proposed an apparatus which is capable of satisfactorily recording data information by providing an amble signal period at the beginning and end portions of each recording area in which data is recorded at one time by using the DAT (refer to Japanese Patent Application No. 61-314922) which corresponds in part with U.S. Patent Application No. 133,010 filed Dec. 15, 1987. This apparatus, however, has to re-record all the data recorded in the previous recording operation, so that if there is a large amount of data, a long period of time is necessary to reproduce and record the same.
As described above, when a conventional DAT is used as a data recorder, there is the problem that the previously recorded data cannot be easily recorded again and so on.
The data signals recorded by the DAT include an error correcting code such as a Reed-Solomon code or the like. Furthermore, because the DAT is intended to record audio signals, i.e. a more or less continuous analog signal, the data errors can be easily compensated for by interpolation techniques, such as previous value holding or the like, even if the errors cannot be corrected by the error correcting code.
However, when the DATA is used as a data recorder, data compensation by interpolation techniques such as previous value holding cannot be effected because of the discontinuous nature of digital data, so that erroneous data can no longer be reproduced unless errors are corrected by the error correcting code.